Police fired teargas and beat supporters of a Sudanese woman facing 40 lashes for wearing trousers in public shortly before her trial was adjourned this morning.

Police in Khartoum moved in swiftly and dispersed about 50 protesters, mostly women, who were supporting Lubna Hussein, a former UN worker charged with "indecent dressing" in violation of the country's Islamic laws.

Some of the women demonstrators wore trousers in solidarity with Hussein. "We are here to protest against this law that oppresses women and debases them," said Amal Habani, a female columnist for the daily newspaper Ajraa al-Hurria (Bells of Freedom).

Hussein's trial was later adjourned until September by a judge to seek clarification from Sudan's foreign ministry over her status.

At the time of her arrest, Hussein was working for the media department of the UN mission in Sudan, which gives her immunity from prosecution. She submitted her resignation after her trial began last week because she wanted to go on trial to challenge the dress code law.

A defence lawyer, Jalal al-Sayed, said the judge wanted to know whether Hussein still had immunity because her employers were still to accept her resignation.

The trial is seen as a test case of Sudan's harsh indecency laws.

Hussein, a widow in her 30s, was arrested with a dozen other trouser-wearing women at a restaurant on 3 July. Ten of the women accepted the punishment of 10 lashes, but Hussein and two others did not.

She sent out hundreds of cards inviting people to her trial and has used her case to campaign against the strict dress codes that exist despite the large cultural differences between northern Muslims and mainly Christian southerners.

Hussein, who is a Muslim, says the decency laws are not consistent with Islam. Her case has drawn support from some women's groups in Sudan, and dozens of women attended last week's hearing.

Hussein, who wore the same trousers to court as on the day of her arrest, said she was resigning from her job to have the chance to prove her innocence.

Public order cases usually involve quick summary trials with sentences delivered shortly afterwards.

"I am ready for what may come," Hussein said earlier. She said the protesters showed that "Sudanese women from different political parties and groupings stand with us".